Inconsistent OAL


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candt
August 18, 2004, 10:57 AM
Hi guys. Just finished loading my first 20 rounds of .223. The load is as follows....lake city brass, once fired from my ar, Remington 7.5 primers, 23.4 gr of AA 2230, winchester 55 gr FMJBT bullets, and an oal of 2.230. At least thats what I shot for. Everything went just fine except for my oals. They range from 2.218 to 2.232. Any idea why I would get such a huge variance? I am used to a variance of +/- .003 or so when loading my pistol cartridges, but this is way beyond that. Are they going to be safe to shoot in my ar? I was planning to go to the range tomorrow to check them out, but I have to check here first, because Im not sure if they are safe. I need to figure out why my oals were so far off, so I can fix this for next time. The bullet seating die is from RCBS.

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moredes
August 18, 2004, 11:13 AM
If you didn't crimp them, try reseating them again. (I know it's not likely that you didn't crimp.) This same thing happened to me on a Dillon press (with a variance of .017"), and then again on a Hornady press (variance of .010"). The first time I thought it was the slop in the Dillon, but the Hornady was damn near new. The Hornady gave me more consistent OAL's, but still, they weren't dead on, varying by as much as .010" . I took my time for the next lot on the Hornady and was very deliberate; I physically felt the press bottom out solidly; the variance was reduced to .004", with the majority hovering between .001-.002". I dunno if this is good or bad; I was using a Redding Competition Seating die in my setup. I dunno how good the RCBS die is.

I don't mean to hijack your thread, but is it possible to crank out ammo that is balls on the OAL setting with even +- .001" variation?

30Cal
August 18, 2004, 01:58 PM
OAL is important in that the rounds need to fit in the magazine. As far as accuracy, the distance between the ogive and the lands is what is important. Bullets will differ from one to the next. Most seating dies contact the bullet on the ogive, not on the very tip (a good thing). Some variation in OAL is expected (but yours sounds excessive).

Are you using a progressive press? Sometimes, depending on how things are adjusted, the presence (or absence) of a round in one station may alter the distance that the press travels.

Mal H
August 18, 2004, 02:33 PM
To answer the most important question you asked: "Are they going to be safe to shoot in my ar?" Yes, they are perfectly safe to shoot in your AR. That OAL variance doesn't get close to anything dangerous.

As for the variance itself, the others have given the most probable answers.

1) The bullets may have some variations at their tips. You seat using the ogive or near the ogive, you measure the OAL from the bullet tip.

2) You may not be seating each and every round with the same amount of pressure. Could be due to press design, variable amounts of lube on casing, handle pressure, etc.

Frankly, I have seen more than .014" variation in factory rounds. I wouldn't worry too much about it, but it would be good to find the cause and correct it.

candt
August 18, 2004, 04:03 PM
Just got back from the range, and fired them all through my AR, and all went well. Accuracy was good too. The brass didnt show any signs of excessive pressure, although the brass seemed a little pale in color? Not sure what thats all about. I measured a bunch of the bullets, and they varied about .012", so it is the bullets that are giving me the OAL's, not the procedure. Does it really matter if some bullets are longer than others? I would think the distance from the lands to the ogive is what really matters. I did a little research on another forum, and discovered that this kind of variation is perfectly normal, so I wont be worrying about it. I am using the lake city brass, and have heard some people say that since this brass is thicker, to lighten my load by 10%. I have also heard some say dont bother. I didnt bother, but would like to hear more opinions on it. I also didnt crimp the rounds, as it seems a lot dont bother with this step either. I am happy with the results, but would like to know more about the paleness of the brass. Thanks again.

30Cal
August 18, 2004, 04:49 PM
in a batch of FMJBT, I'd expect some variation. We're talking about fodder ammo here, not an expensive box of Sierra Matchkings.

Mil brass does have less volume than commercial, so it does make sense to back off some. I don't shoot a lot of .223 so I don't know where you're at w/ your load.

I don't usually crimp ammo (semi-auto included) unless I've got evidence that the case mouth is too loose (and then it's better to fix the sizing die).

I think I know what you mean by the brass looking paler. All I can say is that I ignore it.

candt
August 18, 2004, 05:30 PM
Thanks for the replys. The load I was using was a starting load, but I will still back off a little, and see what happens. Im not going to crimp either. I seated my first bullet way too deep, and it took several hard whacks to get it out, so neck tension seems to be fine.

Ive got another question about chamfering....is it possible to chamfer too much? I use the lee case trimmer, and chuck the shell holder in a drill, and after sizing, I would touch the mouth with a chamfer tool. However, never seeing anyone do this, I dont know if I chamfered too much, or if this is even possible, nor do I know what the effects of it would be if it were possible. Thanks again for the replys. I'll experiment with some lighter loads, and test them out. BTW, I am using a wilson headspace guage to help me set up the sizing die. Great little tool for those who havent tried one.

Mal H
August 18, 2004, 05:43 PM
Now that you've shot them, I must add - Wait - they could blow up your gun!

Sorry, had to do that. :)

How did you like the flash from the AA2230? I've found that I usually need sunglasses with that powder. It's a good, if not perfect match for .223, but it sure has an industrial strength afterburner!

On chamfering - Yes, you can chamfer a case too much. Just a touch is all it takes to leave a nice bevel on the inside of the mouth. Too much and you can shorten the purchase on the bullet and weaken the tip of the mouth.

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